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Image Loader Registration

This example shows how to register custom image loader so that library functions such as GP_LoadImage() and GP_SaveImage() can use it.

/*****************************************************************************
 * This file is part of gfxprim library.                                     *
 *                                                                           *
 * Gfxprim is free software; you can redistribute it and/or                  *
 * modify it under the terms of the GNU Lesser General Public                *
 * License as published by the Free Software Foundation; either              *
 * version 2.1 of the License, or (at your option) any later version.        *
 *                                                                           *
 * Gfxprim is distributed in the hope that it will be useful,                *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of            *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU         *
 * Lesser General Public License for more details.                           *
 *                                                                           *
 * You should have received a copy of the GNU Lesser General Public          *
 * License along with gfxprim; if not, write to the Free Software            *
 * Foundation, Inc., 51 Franklin Street, Fifth Floor,                        *
 * Boston, MA  02110-1301  USA                                               *
 *                                                                           *
 * Copyright (C) 2009-2012 Cyril Hrubis <metan@ucw.cz>                       *
 *                                                                           *
 *****************************************************************************/

 /*

   Shows how to register custom image loader/saver.

   Feed it with small image (cca 60x60 pixels) to produce ascii art version.

  */

#include <stdio.h>
#include <string.h>
#include <errno.h>

#include <GP.h>

/*
 * Saves 2 bpp grayscale image as ASCII Art
 */
static int save(const GP_Context *img, const char *dst_path,
                GP_ProgressCallback *callback)
{
        if (img->pixel_type != GP_PIXEL_G2) {
                errno = ENOSYS;
                return 1;
        }

        FILE *f = fopen(dst_path, "w");

        if (f == NULL)
                return 1;

        unsigned int i, j;

        for (j = 0; j < img->h; j++) {
                for (i = 0; i < img->w; i++) {
                        GP_Pixel p = GP_GetPixel_Raw(img, i, j);

                        switch (p) {
                        case 0:
                                fprintf(f, "  ");
                        break;
                        case 1:
                                fprintf(f, "..");
                        break;
                        case 2:
                                fprintf(f, "()");
                        break;
                        case 3:
                                fprintf(f, "OO");
                        break;
                        }
                }

                fprintf(f, "\n");

                if (GP_ProgressCallbackReport(callback, img->h, j, img->w)) {
                        fclose(f);
                        unlink(dst_path);
                        errno = ECANCELED;
                        return 1;
                }
        }

        if (fclose(f))
                return 1;

        GP_ProgressCallbackDone(callback);

        return 0;
}

GP_Loader loader = {
        .Load = NULL,
        .Save = save,
        .Match = NULL,
        .fmt_name = "ASCII Art",
        .extensions = {"txt", NULL},
};

int main(int argc, char *argv[])
{
        GP_Context *c, *gc;

        GP_LoaderRegister(&loader);

        /* List all loaders */
        GP_ListLoaders();
        printf("\n\n");

        if (argc != 2) {
                fprintf(stderr, "ERROR: Takes image as an argument\n");
                return 1;
        }

        /* Now load image and save it using our loader */
        c = GP_LoadImage(argv[1], NULL);

        if (c == NULL) {
                fprintf(stderr, "Failed to load image: %s\n", strerror(errno));
                return 1;
        }

        gc = GP_FilterFloydSteinbergAlloc(c, GP_PIXEL_G2, NULL);

        if (gc == NULL) {
                fprintf(stderr, "FloydSteinberg: %s\n", strerror(errno));
                return 1;
        }

        printf("Saving to test.txt\n");

        if (GP_SaveImage(gc, "test.txt", NULL)) {
                fprintf(stderr, "Failed to save image: %s\n", strerror(errno));
                return 1;
        }

        return 0;
}